British Foreign Secretary David Miliband spoke at the Massachusetts Institute of Technology, his alma mater, on international efforts to rebuild the Afghan government.
Miliband said military and political efforts in Afghanistan must work hand-in-hand so there is room for the Afghan government to grow.
International leaders included a reconciliation process with moderate members of the Taliban in order to reverse years of declining government influence.
"The Afghans must own, lead and drive such political engagement," said Miliband." It will be a slow, gradual process."
Miliband said political measures in Afghanistan need "clarity" to persuade Taliban and al-Qaida insurgents to abandon their armed struggle and accept the validity of the emerging Afghan government.
"As (U.S.) President (Barack) Obama put it, 'We are not going to succeed simply by piling on more and more troops,'" he said.
The British foreign secretary added that Afghan progress required an "honest acknowledgment" from the region as well.
Afghan President Hamid Karzai has called for a tribal meeting April 29 to discuss building a political framework.